Studies Of Ovine Ruminal Microbial Community In Response To Different Diets And Bacterial Lipopolysaccharide Impact On Ex Vivo Ruminal Explants

Sheep are an essential part of the world-wide agricultural economy.Mainland China has changed dramatically from the top three producers in 1961 to the top first in 2014.This thesis has disclosed the microbial community and their products,including lipopolysacharide(LPS).Nutritional intervention implementation at an early age can impact adult health and performance in ruminants,including sheep by changing the developmental profile of the gut microbiota.We delineated the impact of various dietaries on ruminal microbial conmnunity exploiting Illumina MiSeq platform.Tewelve one-week-old lambs were divided into four groups as follows:breast milk-fed lambs-only-suckling milk without receiving any ration(group 1);concentrate feed-fed lambs(group 2);grass fed lambs(group 3);concentrate and grass-fed lambs(group 4).Ovine ruminal fluids were collected for pH value measurements and microbial community isolation.Our results showed the ruminal pH values remained largely within normal limits.Furthermore,the ruminal bacterial communities were more diverse in the grass feed-fed group in comparison with the other groups,as each group had a distinct microbiota.To study the immediate immune response of ruminal mucosa in response to bacterial toxins,such as LPSSalmonella typhimurium lipopolysaccharide,we have set up an ex vivo ovine ruminal model,which can mimic the multicellular process to explore the early steps in(LPS)stimulation using RNA-seq technology.Ovine ruminal explants were collected for histological and transcriptional analysis and supernatants collected to quantitate lactate dehydrogenase(LDH)enzymes.A total of 8 and 523 genes were significantly over-expressed between LPS-treated and control tissues at 6 and 12 h,respectively.However,six and seven hundred and thirteen genes were significantly downregulated between the aforementioned tissues,correspondingly.Key genes up-regulated in response to the addition of LPS were tumor necrosis factor(TNF),interlukin(IL)-1 beta(b),IL-6,IL-8,IL-17B,IL-19,MMP-1,MMP-3,and integrin alpha 2(ITGA8,9).Overall,these results indicate that nutritional intervention implementation at an early age plays a crucial role in shaping ruminal microbial community composition,and diversity.Furthermore,this study shows for the first time that galectin-1 is up-regulated in an ex vivo ruminal segment model exposed to bacterial lipopolysaccharide following 6 h of incubation,and the ruminal segment model has been shown to be a suitable tool to study the bacterial lipopolysaccharide effects on the ovine ruminal tissues prior to in vivo assessment.